Epitaxial growth of tungsten nanoparticles on alumina and spinel surfaces

摘要

Isolated tungsten nanoparticles (alpha-W and beta-W phase) were synthesized and epitaxially grown on alumina and spinel particle surfaces with an average tungsten size of <= 20 nm for a low tungsten content (of <= 1.5 vol%). Using tungsten (VI) ethoxide alcoholic solutions, tungsten trioxide hydrated precursors were attached to a ceramic grains surface as a nanoparticle coating. High-resolution transmission electron microscopy (HRTEM) micrographs showed epitaxial interfaces between alumina, spinel and metallic tungsten. This epitaxial growth is assumed to be due to the effect of water vapour on the sublimation of ortho-tungstic acid during the reduction process in a hydrogen atmosphere. The planes involved in the epitaxy were found to be (2 (2) over bar0)(Al2O3) parallel to(121)(W) and (311)(MgAl2O4 parallel to)(110)(W).